IP stands for Internet Protocol. IP address is a unique number which is used to identify device within a network. Every device connected to a network (the Internet is a network too) must have IP address in order to communicate with other devices on the network. IP addresses are usually represented in dot-decimal notation: four numbers, each ranging from 0 to 255, separated by dots, e.g. 123.123.123.123

No. Internet service providers (ISP) do not assign constant IP addresses to their customers because, unlike in the case with phone numbers, there is a limited number of available IP addresses. Instead, some ISPs shuffle internet IP addresses among currently connected customers as often as every several hours; others might leave them unchanged for days. By doing so ISPs decrease the number of IP addresses they need to use to serve their clients.

As a result, IP addresses are not assigned to some particular street or house but to a rather broad geographical region. However, in most cases it is possible to narrow the possible geographical location of an IP address down to 25 mile radius.

No. Email address is not associated with any geographical or IP address. Mail servers can usually be accessible from anywhere in the world by any number of people who know the password. Email service providers do know from what IP some certain email was sent but this information is normally kept private and is not legally obtainable (unless you have a warrant from court to obtain this information and the mail servers are in the country where this warrant can be enforced)